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2

  1. I was wondering if the following two ways of running a bash script are equivalent?

    . ./myScript.sh

source myScript.sh
  2. Are they both running the content of the script instead of running the script, i.e. not creating a subshell for running the script?
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Hey, that's in the manpage! – alex Aug 1 '11 at 18:37
@alex: show me please? man ., man source or whatever I haven't know yet. – Tim Aug 1 '11 at 18:39
2  
See type . and help . – rozcietrzewiacz Aug 1 '11 at 18:43
man $SHELL, /source – alex Aug 1 '11 at 20:42
3  
. is more portable according to others. – l0b0 Aug 2 '11 at 10:49

2 Answers

up vote 12 down vote accepted

  1. They are equivalent in bash in that they do exactly the same thing. On the other hand, source is 5 characters longer and is not portable to POSIX-only shells or Bourne whereas . (dot) is, so I never bother using source.

  2. That is correct - sourcing a file runs the commands in the current shell and it will affect your current shell environment. You can still pass arguments to the sourced file and bash will actually look in $PATH for the file name just like a normal command if it doesn't contain any slashes.

Not related to the original question of . vs source, but in your example,

. ./myScript.sh

is not identical to 

source myScript.sh

because while . and source are functionally identical, myScript.sh and ./myScript.sh are not the same. Since ./myScript.sh contains a slash, it's interpreted as a path and the shell just uses ./myScript.sh. However, myScript.sh does not have a slash so the shell does a $PATH search for it first. This is the POSIX specified standard behavior for .. Most shells default to this although they may add extensions (such as searching in the current working directory after the path search) or options to change the behavior of ./source.

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the behavior when the provided path of the file doesn't contain a / is shell-dependent and for bash and zsh depends on whether the POSIX mode is enabled or not. Also note that in many ksh implementations, . behaves differently from source. – Stephane Chazelas Dec 14 '12 at 20:12
@StephaneChazelas Yes, you are right. I added a note to clarify that it the above description is of the POSIX standard. – jw013 Dec 14 '12 at 20:21
up vote 4 down vote

Yes, they are equivalent. There is no functional difference; . is just a builtin synonym for source.

(Edit: Apparently this is only true for bash and zsh. Some lighter shells don't have source, only . is specified by POSIX so ksh, dash, ash, etc. may not have source. See jw013's answer for info.)

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Thanks! But $ alias . outputs bash: alias: .: not found . – Tim Aug 1 '11 at 16:57
That is they are both builtins and the alias is builtin too. This is documented, but I guess 'synonym' is the right term in this case, not 'alias'. – Caleb Aug 1 '11 at 17:00

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